All 19 people on board the Super Puma EC 225, part of the CHC Helicopters fleet, were rescued safely.

The incident happened off Fair Isle, about 32 miles south of Shetland, and the alarm was raised at about 15:30.

The helicopter had been heading to the West Phoenix drilling rig, west of Shetland.

A spokesman for CHC Helicopters said: "All 17 passengers and two crew have been picked up by the standby vessel Nord Nightingale following the controlled ditching."

He added: "All 19 people on board are safe and well.

"CHC's primary objective is always the safety of our passengers and crew, and our pilots' actions today are consistent with that.

"The flight was being operated on behalf of Total."

Those on board the helicopter have praised the pilots for the way they handled the incident.

Passenger Michael Mashford said: "It's strange because yes, I was afraid, but all the training that we do kicked in.

"Everybody was very very calm. One of the guys that's normally one of our rescue guys, he's very cool, calm and collected and he kept people calm and we did everything that's expected of us.

"We all got into the rafts, got away from the helicopter. No problems at all."

Nick Mair, regional vice president of western North Sea at CHC, said: "Plans are under way for the recovery of the aircraft.

"We are temporarily holding flights using the same type of EC225 aircraft pending receipt or confirmation of certain information from the crew involved in today's incident and technical follow-up."

In May, all 14 people on board a Super Puma EC 225 were rescued when their helicopter came down around 30 miles off the coast of Aberdeen during a flight to an oil rig.

Jake Molloy, from the RMT union, said: "Coming so soon after another ditching, and culminating in four incidents in the space a little over three years, it's bound to cause a bit of concern on the ground.

"I think what's absolutely vital now is to get communications out to reassure the workforce and their families, that their means of transportation to and from their work is safe."

Survival training

Bob Lauder, industry body Oil and Gas UK's health and safety policy manager, said: "Oil and Gas UK is pleased to hear that all 19 people on board this helicopter have been successfully rescued.

"This is testament to the skill of the pilots, as well as the comprehensive survival training which all offshore workers must undergo to prepare them for this type of situation.

"We now await more information on the cause of this incident."

Balpa, the union which represents professional pilots, praised the actions of the helicopter crew.

A spokesman said: "Today's incident again highlights the importance of trained flight crew. We are in contact with the two members concerned to offer them our full support.

"It appears that the pilots performed a controlled ditching into the North Sea which is an extremely challenging manoeuvre.

"The ultimate aim of a ditching is to ensure that all the passengers and crew get to safety, which is exactly what has happened in this case."